turn down - Idioms - by the Free Dictionary, Thesaurus and Encyclopedia.
turn someone down
to issue a refusal to someone. We had to turn Joan down, even though her proposal was okay. We turned down Joan, even though her credentials were good.
See also: turn
turn something down
1. to bend or fold something down. He turned his coat collar down when he got inside the house. Timmy had turned down his cuffs and caught one of them in his bicycle chain.
2. to decrease the volume of something. Please turn the radio down. Can't you turn down that stereo?
3. to reject something; to deny someone's request. The board turned our request down. She had turned down John's offer of help, too.